here - Active Audio
Contents
1. 35 10 Mechanical and electrical characteristics of StepArray columns 36 List of Figures 44 10 11 12 13 14 15 16 17 18 19 20 Direct sound increases speech intelligibility reverberated sound impairs it 5 ASADO Wave INE sr aa pas han Reed EE LORS bu E she a a E 7 Electronic and geometi AMAS e s eoa ck Le a da pics A ee Y 8 DOR DMG 2 a ange ent fn Bae du A er du Het t n 9 Example of StepArray system 10 Listening zones PMGORS lt lt 4 22 koe nu A Ra mg e a ee E RU Re A 11 Listening zones S models 11 Shared electronics example 12 Listening area definon oscura le ER RA Has Rue ame he na 13 Interferences between columns 15 Rear panel of the UT26 processor 2 16 SVOP ISO 24 56 ts DEP Rd ELE ee ete bab wd 17 SAdrive directivity block ee LA be ee due ee a 17 Examples of a CAD modeling results 18 Gol MOUNINO Ona Wall cea kee Le On a A AA 21 LIT26t0 MMPAGISO MO o e 4 02 oe a aa aa a LE papa 4 22 IMPABISO amplller Setup i dba db de a a de bn e Be A weg es we 22 IMPABISO Eo Colum Wing ice a Bn a a aa a ee a A EE ee ee ge pla 23 Pisces MOMENT bls Gh gk ee SE Ne a ee ce ed ee eA ok A GR G 24 RS232 wiring standard DB92. For further information see the MPA6150 owner s manual Last update December 23 2010 33 Aline audio 14 3 Subwoofers characteristics 14 3 Subwoofers characteristics Acoustical data Frequency bandwidth 40 500Hz Type Bass Reflex Max SPL at 1m 130dB Peak Sensitivity 97dB 1W 1m Directivity Omnidirectionnal Loudspeaker 12 neodymium Electrical data Power handling 450W AES Inputs SA12 SW Dual Speakon SA12 SWA 2x XLR sym OdBV Impedance 80 Amplification SA12 SW Compatible with MPA 6150 amplifier SA12 SWA Digital amplifier Class D Electrical connection Neutrik Powercon 195V 250V AC 50 60Hz Mechanical data Materials Plywood Dimensions 435 x 400 x 440mm Weight SA12 SW 18 5kg SA12 SWA 19 8kg Color Black Tuning and exploitation Software Supplied SAdrive software Filtering processor UT26 with SUB option FR filtered by processor UT26 e ER at 1m i 50 100 Frequency Hz 200 Figure 23 SA12 SW frequency response 7Only for SA12 SWA 34 y audio 14 4 Columns characteristics 14 4 Columns characteristics 14 4 1 Electrical characteristics of StepArray columns Channel 1 2 3 4 5 6 SA100P 6 60 6 60 6 60 _ _ _ SA180P 6 60 6 60 6 60 _ SA250P 6 62 6 60 6 60 440 440 4 40 SA400P 6 62 6 60 6 60 6 60 6 60 6 60 S
3. Log in Admin mode Structure E L Enter off line mode Add virtual processor 12 Advanced functions 12 1 Automatic gain control AGC Automatic Gain Control is available if the UT26 processor is equipped with the MIC option section 5 1 AGC allows automatic adjustment of the diffusion level according to the sound level captured by the microphone when no message is played Using this function the sound level perceived by listeners is adjusted for optimal comfort moderate level when the ambiant noise is low higher level when the ambiant noise is high in order to provide good intelligibility The amplitude of the ambiant noise captured by the microphone is smoothed with a time constant adjustable by the user This resulting smoothed value is used as a basis for gain calculation below a threshold adjustable by the user the AGC gain is set to 0d B above this threshold the AGC gain increases proportionally to the ambiant noise up to 12dB For example If the ambiant noise is 75dBspz and the AGC enters in action Threshold at 654Bsp1 then the AGC gain will be 10dB i e 75dB 65dB e If the ambiant noise is 80dB sp and the AGC enters in action Threshold at 65d B spz then the AGC gain will be 12dB i e 80dB 65dB 15dB but AGC gain is 124B max The AGC algorithm is summarized on figure 21 AGC gain dB A 12 rennes ts 0 a E Ambiant noise E dB spl Threshold Threshold 12dB Fi
4. Power is uniformly distributed to all loudspeakers This way they can all be used at their maximum capabilities enhancing overall performance and sound pressure level The number of channels does not depend on the number of loudspeakers Therefore many small full range loudspeakers can be used to obtain perfect sound quality in the treble range and reduce secondary lobes at higher frequencies 2 Overview of the StepArray system The StepArray range consists of several column models dedicated to speech diffusion and to mid power music diffusion in large and or reverberant enclosed spaces The different models allow coverage of flat or tilted audience area ranging from 15m to 68m with perfect speech intelligibility and high sound quality Last update December 23 2010 9 y audio 2 1 StepArray system example StepArray columns use external electronics They are controlled by the UT26 digital signal processor DSP and powered by the MPA6150 6 channel amplifier Having external electronics has the following advantages e Possibility to use a single UT26 processor controling several columns yielding a large cost reduction see section 2 3 on the next page e Possibility to use several amplifiers for a single column in order to increase security failure of one amplifier would only affect some of the channels but the column continues to diffuse messages For example when using 2 columns and 2 amplifiers amplifier 1 can be connected t
5. audio 11 SAdrive software The SAdrive software is used to tune all the filtering parameters of StepArray columns it is available as free down load here http www activeaudio fr en gamme steparray sadrive 11 1 Init new processors When a new processor factory settings is first connected to SAdrive it needs to be initiated The initalization steps are described below Switch OFF all processors Connect to COM port z Bi SAdrive 208 File Activesetup Presets Administration Help Log in administrator mode E Sadrive 208 RIE File Activesetup Presets Help Log in Admin mode Choose COM port R SSS Supervision po Structure Processor software update Switch ON the processor connected with CV232 Structure Set initial parameters for this processor then apply Set initial parameters for this processor then apply Processor address must be unique Repeat step 6 and 7 for each other processor 26 Log in Admin mode Choose COM port SSS Supervision Processor software update Gl Add new processor eax UT26 Identification UT25 name Address Column ouput on channels 1 to 6 Activate Name sa250p 1 Group hall An unused processor has been detected you can now specify its properties 1f you don t want to use this processor unplug it from the BAN or shut it down To prevent conficts make sure to turn only one virgi
6. a du du pa au ge au y 15 Acoustical data ISl Common data ios dope LA CR ae eee dns he RE sens eee 15 2 BAMUP acoustival data lt 5 4 5 ae d RARER BU BAM RE ME R E 15 3 SALSOP acoustical data 2540 66 dun ee he jeton a ee ee Ewe 184 SACSUP acomstical data avoid esa D deu Banni A a 15 5 SAAQUP aponstical data op cie o mb a A a do ae 15 6 SA1805 acomstical data 2c dut NO EA osas ce die dut BR a ER Ew dure 15 7 BA2D0S acoustical data 2 des db Du Le D Rede bebe eh D eh be Gees List of Tables List of Figures 21 22 22 22 23 23 24 25 25 26 26 27 27 27 28 29 30 30 32 32 33 34 39 37 37 38 39 40 41 42 43 44 44 20 Aline audio 8 Installation of the columns StepArray columns are mounted verticaly usually on a wall using the supplied brackets Figure 15 illustrates the steps to follow for column mounting See also figure 25 on page 36 for technical drawings of the brackets Place the 2 brackets on the wall using 8mm diameter screws Column height 5mm Mount the column using the supplied nut and screw Figure 15 Column mounting on a wall It is important to ensure verticality when mounting StepArray columns Last update December 23 2010 21 Active audio 9 Wiring 9 1 UT26 processor to amplifier A UT26 processor can be connected to one or several StepArray columns via amplifiers see figure 16 When a
7. and a daughter board placed inside the UT26 processor which supplies phantom power on input 2 of the processor The microphone output of the column should be linked to input 2 of the UT26 processor using a shielded conductor pair Wiring is described in table 5 GND Pin1 Pin2 Pin3 Table 5 Wiring of the microphone standard XLR Last update December 23 2010 23 V audis 9 5 RS232 wiring 9 5 RS232 wiring Only one processor should be connected with RS232 to the computer If there are several UT26 processors then communication with all processors is possible when the BAN connectors are connected in daisy chain This is illustrated in figure 19 Computer is connected to UT26 with CV232 option Wcv232 OMIC OisuB__Osss DB9 female female null modem cable BAN848 Audio Bus UT26 processors are connected by the BAN Figure 19 RS232 wiring diagram RS232 wiring uses standard DB9 null modem wiring as shown in figure 20 Figure 20 RS232 wiring standard DB9 null modem When several UT26 processors are used they can be inter connected by the BAN connector In this case y only one of the UT26 connected to the BAN must be fitted with the CV232 option The CV232 option is disabled by putting the JP1 jumper of the CV232 board to PC position When the distance between the computer and the processor is over 30 meters it is possible to use an RS485 port co
8. e Ensuring proper SPL coverage e Delivering satisfying intelligibility of vocal messages Avoiding echoes and feedback effects e Giving the feeling that the sound comes from the speaker The positioning of columns should follow a few basic rules Use as few columns as possible choose the column covering as much of the listening area at once Add more columns only if necessary Beware intelligibility could be impaired if there are too many columns Columns should be placed so as to obtain the most homogeneous sound level over the audience area For complex cases it is highly recommended to use CAD software which will take into account the acoustics of the room CAD tools are presented in section 7 5These maximum cable lengths correspond to a sound level loss of 3dB 14 Aline audio e Place the columns as close as possible to the nominal altitude see table 2 on page 13 When placing columns at non nominal altitude use SAdrive software to check that column emission will be acceptable When dealing with several columns the differences of propagation distances for columns covering the same listening area should be less than 20m so as to avoid possible echoes for certain sections of the audience See figure 10 Column 1 Column 2 U If d1 d2 lt 20m there is no echo UO Listening area Listener Figure 10 Interferences between columns Also consider microphones and stage e the speaker must be pl
9. enough energy to cover the noise In large spaces changing the reverberation time involves changing a significant portion of the wall material and most of the time this is not possible Providing a strong signal to noise ratio is also important but it is not enough to ensure intelligibility Therefore in large and reverberant rooms the most important parameter the public address must affect is the Direct Sound H foe i i Reverberated Sound Patio It is necessary to privilege the direct sound energy and avoid putting energy in the reverberated part of sound This can be achieved either by moving the loudspeaker close to the listener or by using highly directional loudspeakers QB In a large and highly reverberant room it is necessary to privilege the direct sound energy for good intelligibility results In large spaces if the loudspeakers are to be placed close to the listeners many loudspeakers are required This is not practical in such places because fixing loudspeakers can be difficult very high ceiling etc Also in many cases this will not give good intelligibility results because only the loudspeakers close to the listener contribute to the direct sound while all the loudspeakers contribute equally to the reverberated sound Several indexes have been proposed to measure speech intelligibility The most widely used of them is the Speech Transmission Index STI Value 0 corresponds to extremel
10. off for music diffusion e The time variant nature of the algorithm used is not compatible with standard anti larsen products Last update December 23 2010 29 Aline audio 12 4 Remote control 12 4 Remote control It is possible to control UT26 processors using a remote controller The only requirement is being able to send hexadecimal code on RS232 connection For example remote controller model Extron MLC 104 can be configured to control UT26 processors Table 7 present the list of accessible operations with their corresponding hexadecimal code 13 Troubleshooting Operation Hexadecimal code Mute 81 Un Mute 82 Increase gain 2dB 83 Decrease gain 2dB 84 Load preset 1 85 Load preset 2 86 Load preset 3 87 Load preset 4 88 Table 7 Remote control character codes Symptom The green switch of the UT26 processor is not ON Possible cause A fuse is burned Solution Replace fuses in power supply connector at the back of UT26 processor 160mA delayed fuses No sound comes out of the column No input signal detected Check that the Sig LED is ON in SAdrive s Status frame If the LED is OFF check that the Input threshold is not too high The UT26 processor is not inited Follow the steps presented in section 11 1 on page 26 to init processors with SAdrive The computer to UT26 cable is defective Check that RS232 cable is wi
11. on the listening area 42 y audio 15 7 SA250S acoustical data 15 7 SA250S acoustical data a SA2508S vertical directivity sound level for the voice octaves 500Hz 1kHz 2kHz in the vertical median plane 5dB OdB 5dB 10dB 15dB 20dB b SA250S horizontal directivity sound level for the voice octaves 500Hz 1kHz 2kHz on the listening plane SPL dist SA250S 15 7 7 250Hz 500Hz 10 1000Hz 2000Hz 4000Hz 5 8000Hz i i i i i 0 5 10 15 20 25 30 c Sound level by octave in the axis of the listening plane in front of the column with respect to the distance from the column Figure 33 SA250S acoustical data 13 Column is in nominal position Levels are referenced to the mean SPL on the listening area Last update December 23 2010 43 audio LIST OF TABLES List of Tables 1 General characteristics of StepArray columns 12 2 Specific characteristics of StepArray column models 13 3 Wiring recommendations for StepArray columns 14 4 AUR 16 Wago WI 25 52 eee ew ee he beh he due de aan a bP ea bee ee ed 22 D MAGO MS MIC s se io sa sara du ee A A ee RR ee Oe G 23 Bb SUBwingon BOL POM cee eed A owe ra ds a 25 7 Remote control icharacte codes cocos a dog we eG es a 30 9 DC resistance of StepArray columns
12. real situation see figure 9 on page 13 The column model in SAdrive doesn t match the real column model Correct the column model using the menu Active Setup Manage processors No bass signal on SUB output The SUB option has not been selected in SAdrive Check the SUB option using menu Active Setup Manage processors The AGC function is not accessible and the Noise field in the status frame shows The MIC option has not been selected in SAdrive Check the MIC option using menu Active Setup Manage processors The AGC function doesn t work and the Noise field in the frame Status shows 40dB The microphone is not properly connected to input 2 of the UT26 processor Make sure the microphone is properly connected on input 2 of an UT26 equipped with the MIC option see section 9 4 on page 23 for wiring Last update December 23 2010 31 Aline audio 14 Hardware specifications 14 1 UT26 processor characteristics Audio data Analog inputs 2 symmetrical inputs connectors XLR F Max input voltage 3 25V 9 5dBU 1st order high pass cutoff at 6Hz Crosstalk lt 90dB Input impedance 15 kQ with option MIC input 2 delivers a 14V phantom power supply Digital input AES EBU 48kHz Analog outputs 6 symmetrical outputs connectors XLR M Max output voltage 1 6V 3 3dBU i e max input of MPA6150 amplifier O
13. 00Hz Fe 2kHz on the listening plane SPL dist SA180P 15 T T 7 T 250Hz 500Hz 10 1000Hz 2000Hz 4000Hz 5 8000Hz 0 5 10 f i i i i i i 0 5 10 15 20 25 30 35 c Sound level by octave in the axis of the listening plane in front of the column with respect to the distance from the column Figure 29 SA180P acoustical data 9 Column is in nominal position Levels are referenced to the mean SPL on the listening area Last update December 23 2010 39 y audio 15 4 SA250P acoustical data 15 4 SA250P acoustical data 10dB 10cB m 10m 20m 30m 40m 50m b SA250P horizontal directivity sound level for the voice octaves 500Hz 1kHz 2kHz on the listening plane SPL dist SA250P 15 7 r 250Hz 500Hz 1000Hz 2000Hz 4000Hz 8000Hz 10 0 5 10 15 20 25 30 35 40 45 j c Sound level by octave in the axis of the listening plane in front of the column with respect to the distance from the column Figure 30 SA250P acoustical data 10 Column is in nominal position Levels are referenced to the mean SPL on the listening area 40 y audio 15 5 SA400P acoustical data 15 5 SA400P acoustical data 10dB a SA400P vertical directivity sound level for the voice octaves 500Hz 1kHz 2kHz in the vertical median plane 10cB
14. 10 10 10 frequency Hz Figure 26 Frequency response column SA250P Average of the mesurements at 7 10 15 20 25 and 30m In red with bass high pass on position 100Hz in blue with bass high pass on position 200Hz 500Hz 0 270 Figure 27 Horizontal directivity column SA250P Last update December 23 2010 37 y audio 15 2 SA100P acoustical data 15 2 SA100P acoustical data 10dB a SA100P vertical directivity sound level for the voice octaves 500Hz 1kHz 2kHz in the vertical median plane 1008 5dB 0dB 50B 10dB 15dB 20dB SA100P horizontal directivity Mes level for the voice octaves AN 1kHz 2kHz on the listening plane SPL dist SA100P 15 T T T T 7 250Hz 500Hz 107 1000Hz 2000Hz 4000Hz 5 8000Hz 0 5 10 J i i i i i 0 2 4 6 8 10 12 14 16 18 20 c Sound level by octave in the axis of the listening plane in front of the column with respect to the distance from the column Figure 28 SA100P acoustical data 8 Column is in nominal position Levels are referenced to the mean SPL on the listening area 38 y audio 15 3 SA180P acoustical data 15 3 SA180P acoustical data 10dB a SA180P vertical directivity sound level for the voice octaves 500Hz 1kHz 2kHz in the vertical median plane 10cB 5dB 0dB 50B 10dB 15dB 20dB SA180P horizontal AA sound a for the voice octaves 5
15. 5dB 0dB 5dB 10dB 15dB 20dB 10m 20m 30m 40m 50m 60m 70m b SA400P horizontal directivity sound level for the voice octaves 500Hz 1kHz 2kHz on the listening plane SPL dist SA400P 16 T T 7 7 T 250Hz 500Hz 1041 1000Hz 2000Hz 4000Hz 5l 8000Hz f i i i i i i i 0 10 20 30 40 50 60 70 c Sound level by octave in the axis of the listening plane in front of the column with respect to the distance from the column Figure 31 SA400P acoustical data 11 Column is in nominal position Levels are referenced to the mean SPL on the listening area Last update December 23 2010 41 y audio 15 6 SA180S acoustical data 15 6 SA180S acoustical data 10dB a SA180S vertical directivity sound level for the voice octaves 500Hz 1kHz 2kHz in the vertical median plane 5dB 0dB 5dB 10dB 15dB 20dB b SA180S horizontal directivity sound level for the voice octaves 500Hz 1kHz 2kHz on the listening plane SPL dist SA180S 15 7 r 250Hz 500Hz 10 1000Hz 2000Hz 4000Hz 54 8000Hz i i i i 0 5 10 15 20 25 c Sound level by octave in the axis of the listening plane in front of the column with respect to the distance from the column Figure 32 SA180S acoustical data 12 Column is in nominal position Levels are referenced to the mean SPL
16. A180S 6 60 6 60 6 60 _ _ _ SA250S 3 30 6 62 6 60 440 440 330 Table 9 DC resistance of StepArray columns For details on connector pin assignement see figure 18 on page 23 in section 9 3 14 4 2 Mechanical characteristics of StepArray columns A 34mm to 55mm Figure 24 StepArray column dimensions Last update December 23 2010 35 y audio 14 4 Columns characteristics Model Dimensions Weight Cable LxWxD mm net shipping SA100P 1024 x 124 x 131 9kg 12kg 4G SA180P 1840 x 124 x 135 17kg 21kg 4G SA180S 1840 x 124 x 135 17kg 21kg 4G SA250P 2505 x 124 x 159 24kg 29kg 7G SA250S 2505 x 124 x 159 24kg 29kg 7G SA400P 4096 x 124 x 135 39kg 46kg 7G Table 10 Mechanical and electrical characteristics of StepArray columns More precise schematics are available on Active Audio s website in several formats S http Awww activeaudio fr en gamme steparray catalogue et telechargements 14 4 3 Fixing brackets 121 51 71 22 OOO cece A A M Red is bottom bracket only Figure 25 Fixing brackets for wall mounting of StepArray columns 36 Aline audio 15 Acoustical data All data presented below is obtained with columns in their nominal position and using nominal DSP filtering param eters flat EQ etc 15 1 Common data amplitude dB
17. StepArray manual Aline audio CONTENTS Contents Contents 2 StepArray tutorial for recommandation 4 1 Sound reinforcement in large spaces 5 2 Overview of the StepArray system 9 3 Choosing the right installation set up 12 4 Column positionning rules 14 5 Options 16 6 SAdrive software 16 7 CAD modeling 17 References 18 ll StepArray technical reference 20 8 Installation of the columns 21 9 Wiring 22 10 Test before powering up 25 11 SAdrive software 26 12 Advanced functions 27 13 Troubleshooting 30 14 Hardware specifications 32 15 Acoustical data 37 List of Tables 44 List of Figures 44 V audio CONTENTS Foreword StepArray is a versatile line array system designed for speech reinforcement in large spaces It offers excellent sound intelligibility slim design external electronics security systems compatibility and more This reference manual is intended to be a user manual for StepArray based systems as well as a complete reference with all the technical specifications and details about the StepArray system How to use this manual This reference manual is divided in two parts e The first part is a tutorial for recommandation It deals with StepArray design and principles introducing the acoustic background necessary to understand sound reinforcement in large space and how StepArray can help to achieve good intelligibility in these places e The second part is a technical reference describing the full range of
18. StepArray products lt covers installa tion wiring maintenance and tuning Extensive technical data is found there Last update December 23 2010 3 Aline audio Part StepArray tutorial for recommandation Table of Contents 1 Sound reinforcement in large spaces 1 1 General issues with public address in large spaces 12 Lkotrdspealelr arta 2152 Des cr A AA A A DS 13 DGRC The Step Array system lt ce ce ro Lou d nude ue nu een 2 Overview of the StepArray system 2 1 StepArray system example o coco so ca co 44 au mas de bn ee 2 2 StepArray column models lt ca ss ss conoces cr teers shoes 2 3 StepArray specificity shared electronics 3 Choosing the right installation set up Bl COMAS pe ta A a ii EA A a SEES Sa PROMIS D co e a A Eee a ES o SO en ae eS A Res OSA EES ne io D a O A A A AO aaa ee E Ek E al ge oe Se Se mei UDO AR eee ee ee a x 4 Column positionning rules 5 Options S1 Mierephone MIC e ece gun Eh ee EE au ERE eR Se eu du 32 Duo bas DUE RUB oc 4 5 a RR ER we ORR RENE A 53 Sound Security System S55 Le ou co ee ee ee dr 6 SAdrive software 7 CAD modeling References 10 11 11 12 12 13 13 14 14 14 16 16 16 16 16 17 18 Aline audio Introduction This is a tutorial for StepArray recommandation Section 1 presents general issues about public address in large spa
19. UT26 is used with several amplifiers to feed several columns with the same signal the inputs are simply daisy chained see figure 16b UT26 MX MW XLR F to WAGO MPA6150 UT26 J MX 6 XLR F to WAGO MPA6150 MPA6150 a Direct wiring b Daisy chain wiring Figure 16 UT26 to MPA6150 wiring XLR F to Wago cables use standard XLR wiring convention as shown in table 4 XLR Wago pin 1 Ground pin 2 pin pin 3 pin Table 4 XLR to Wago wiring 9 2 Amplifier setup MPA6150 amplifiers should be tuned with all gains to max and microswitches set for independent channels as described in figure 17 All gains to max IN3 sreo IN4 Set all microswitches for 6 independent channels Figure 17 MPA6150 amplifier set up 22 y audio 9 3 Wiring amplifiers to columns 9 3 Wiring amplifiers to columns Wiring amplifiers to columns is straightforward simply connect each channel of the MPA6150 amplifier to the corresponding channel of the column and provide a common ground as illustrated by figure 18 6 channel column cabling on MPA6150 amplifier Column output on channels 4 5 6 CH3 CH4 CH5 CH6 Column output ee CH2 CH3 CH4 CH5 co on channels 1 2 3 CH1 CH2 CH3 CH4 OS LD GN Figure 18 MPA6150 to column wiring 9 4 Wiring the microphone MIC option The MIC option consists of a microphone integrated inside the column
20. W J van Beuningen E W Start Optimizing Directivity Properties of DSP Controlled Loud speaker Arrays Reproduced Sound 16 Conference Stratford UK 17 19 Nov 2000 Institute of Acoustics 18 StepArray Technical manual Aline audio Part Il StepArray technical reference Table of Contents 8 Installation of the columns 9 Wiring 9 1 UT26 processor to Amplifier lt 22 25 nes a a ar a od 9 2 Ampliar SUB Le der daa pers o a eed 93 Wiring ampliters to COMME 4 4 4 8 en ea de so ee eS 9 4 Wiring the microphone MIC option Oy RS o 8 Gos ds db ab dun Oe ee D Rd RD Der eek A he ay OG GUB o o se GO D EE DS SERRES SE d SRE RUES Ja 10 Test before powering up 11 SAdrive software 11 1 Init new processors cc dos he wee da mn de dr Ge ewe du me 112 Check connected processors o 24 dub ma dues don da dote die EN 4 ua 12 Advanced functions 12 1 Antomatie gain control AGO exista nude megane spi pe ar 12 2 Security Sound System O de des pus AN 123 Feedback kiler oo 5 ee RR RE RAR RE SAR BAR aa 12 4 Remote comtr l 2 22 2 du Ra RE du he due 13 Troubleshooting 14 Hardware specifications 14 1 UT26 processor characteristics lt rcc ake RRR RR RE HAE 14 2 MPA6150 amplifier characteristics 143 Subwoofers characteristics e os es sos sar bedd HE Ut Dog 4 eu 14 4 Columns characteristics 2 2 su ga ga gun
21. aced at less than 15 m from the columns otherwise he will hear the echo of his own voice e the audience must feel that the sound comes from the speaker This is achieved by fitting a column on each side of the stage so as to re centre the sound A single column can be used but in this case it has to be close to the zone to be covered e Prevent the feedback effect there should never be a microphone aiming at a column this could generate a feedback problem The impact of the room acoustics on the sound level within the covered zone is relatively low since the fun damental aim of the StepArray columns is to provide a strong direct sound in order to ensure high intelligibility O even in reverberant spaces 2SPL reinforcement by reverberation can be higher close to walls 6in this context propagation distance is the column to listener distance Last update December 23 2010 15 Aline audio 5 Options Several options are available for the StepArray system These options bring additional electronic cards within the UT26 processor and the columns A marqued plaque on the back of the processor indicates the options as shown in figure 11 5 3 ei EA 137 gsus _ osss UT26 Processing Unit Made in France Audio Bus BAN848 Local Bus BCL Computer RS232 Figure 11 Indication of options on the rear panel of the UT26 processor CV232 only in this example 5 1 Microphone MIC This option brings a
22. airs it Intelligibility rule 1 7 Direct sound increases speech intelligibility reverberated sound impairs it Last update December 23 2010 5 V audio 1 1 General issues with public address in large spaces Ambient noise Ambiant noise reduces intelligibility For example the loud noise produced by trains in railway stations could prevent the listener from understanding a message properly Also the noise level can change drastically over time in this case the public address system must adjust its diffusion level according to the noise level Eh Intelligibility rule 2 SS The public address sound system should emit at least 104B above the ambient noise level Architectural constraints Loudspeakers positionning is often restricted by architectural or practical constraints Because loudspeakers are not always welcome in places where aesthetics are important they should be made discreet and as few as possible should be used Speech intelligibility in large spaces As seen above speech intelligibility depends on Reverberation time This is a caracteristic of the room acoustics and depends on the material of the wall and the geometry of the room Direct Sound Reverberated Sound distance and loudspeaker directivity energy ratio This depends on reverberation time room volume loudspeaker to listener Signal Noise ratio This depends on the ability of the sound system to emit
23. ces 1 1 and explains how loudspeaker arrays can be a good solution to these issues 1 2 StepArray is introduced as the last point of this section 1 3 The following parts are a step by step introduction to the StepArray system e Section 3 explains the rules to follow when designing a StepArray system Column positionning is described in section 4 The different options are described in section 5 SAdrive software serving both as a simulation and tuning software is described in section 6 CAD modeling tools are presented in section 7 1 Sound reinforcement in large spaces 1 1 General issues with public address in large spaces Speech reinforcement in large and reverberant rooms is made difficult by several causes namely reverberation ambient noise and architectural constraints Reverberation In all rooms sound transmission from a loudspeaker to a listener can be divided in two parts figure 1 Direct sound which depends on the loudspeaker to listener distance and on the loudspeaker directivity Reverberated sound which depends on the geometry of the room and the acoustical properties of the walls In large spaces church railway station the reverberation can be very important and plays a negative role on speech intelligibility Note that the energy of the reverberated sound is constant throughout the room Reverberated a E A Figure 1 Direct sound increases speech intelligibility reverberated sound imp
24. ctions and move them back on a vertical line much like what is done in the Fresnel lenses used in optics Then electronic delays are used to compensate sound propagation delay between the sections It was shown in DGRC Arrays that with this delay setting there is no diffraction at the edges of the saw tooth shape As a result of this principle the number of DSP and amplification channels is independent of the number of loudspeakers so that a dramatically reduced number of channels is achieved Aline audio Y F1 Di Gj gt F2 D2 Y Wave front F3D3 cp A al Input a signal EQ eas F4H Dy 64 gt A gt F5 D5 NS y Fe Dg A gt 5 Figure 4 The DGRC principle used by StepArray columns The wave front is controlled both by the positioning and orientation of the loudspeakers and by filters F delays D and gain G of each channel The main advantages brought by the DGRC principle used in StepArray columns are The column is vertical and can be fitted close to the wall Reduced number of electronic channels both for DSP and amplifiers For example model SA250P which is 2 5m high uses only 6 channels for 30 loudspeakers This can make a big cost difference
25. en designed By specifying the effective positioning of the column and the shape of the listening area in the Directivity bloc of SAdrive the DSP filtering parameters are automatically adjusted to the situation O Choose the column which covers the most of the listening area Figure 9 Listening area definition Model Height Nominal altitude Audience Range 500Hz 2kHz Min distance Channel standing seated audience angle 0 3dB 5dB dmin count SA100P im 2 5m 2 1m Flat 0 5 15m 21m im 3 SA180P 1 8m 2 5m 2 1m Flat 0 5 30m 40m im 3 SA250P 2 5m 2 5m 2 1m Flat 0 59 35m 45m im 6 SA400P am 3 0m 2 6m Flat 0 3 68m 90m im 6 SA180S 1 8m 3 0m 2 6m Tilted 5 20 22m 29m am 3 SA250S 2 5m 4 2m 3 8m Tilted 5 20 28m 36m 4m 6 Table 2 Specific characteristics of StepArray column models 3 2 Processors The UT26 processor has 6 output channels therefore it can deliver signals for two 3 channel columns or one 6 channel column It is also possible to connect two 3 channel columns with different signals on the same processor to obtain a stereo sound Independent settings are available for directivity equalization and delays All these settings can be saved and recalled remotely thanks to presets More details on wiring can be found in section 9 1 3 3 Amplifiers The MPA6150 amplifier is capable of delivering 6 x 150
26. gure 21 Automatic gain control functional graph Last update December 23 2010 27 y audio 12 2 Security Sound System SSS e When the AGC function is used the Input selection of the Input block is forced to Input 1 type analog SS The ambiant noise value is displayed by steps of 2d B in the Status frame of SAdrive 12 2 Security Sound System SSS Security Sound System conformance is available when the UT26 processor is equipped with the SSS option This option includes e daughter boards in the UT26 processor a push button with 2 LEDS on the front panel of the UT26 processor an SSS sensor box The SSS principle of operation is to use a probe signal along with a current sensor to monitor effective current consumption of each channel of the system A UT26 processor equipped with the SSS option adds a high frequency sine component to the audio signal output and synchronously detects this high frequency signal on its analog input 2 where the SSS box is connected This loopback allows precise monitoring of the current consummed by the columns The cabling diagram for an SSS installation is shown in figure 22 optional Ambiant mic To In2 UT26 From To SSS sensor CH3 CH4 CHS CH6 66 Eral NN 7 SSS sensor wiring MPA6150 to column with SSS Figure 22 SSS cabling diagram 28 y audio 12 3 Feedback killer Any malfunction detected by the processor will have
27. iate constant SPL over the listening plan Last update December 23 2010 7 V audio 1 3 DGRC The StepArray system The main characteristic of an array is its range which corresponds to the minimum and maximum distance from the column where the SPL is constant with a given tolerance The range of a column is proportional to its height An other important characteristic of an array is the spacing between loudspeakers Good rejection of secondary lobes at high frequencies is obtained with a short spacing At high frequencies geometric arrays generally use waveg uides that radiates like an isophase vertical slit Aligning several of these waveguides yields a semi continuous line source which greatly reduces undesired secondary lobes Wave front a In a geometric array loudspeakers are aligned b In an electronic array loudspeakers are aligned vertically and along the shape of the wave front to be generated the wave front is synthesized by adequate filtering by filters F de usually a J shape lays D and gain G associated to each loudspeaker Figure 3 Electronic and geometric arrays 1 3 DGRC The StepArray system The StepArray columns implement the DGRC line array principle Digital and Geometric Radiation Control which is a synthesis of geometric and electronic arrays patented by Active Audio The principle is illustrated in figure 4 on the facing page The key idea is to split the desired wave front into se
28. n electret microphone in the connection box at the back of the column and its phantom power supply delivered through input 2 by the UT26 processor This option is needed to enable the AGC automatic gain control function section 12 1 5 2 Sub bass Output SUB When playing music it is generally necessary to complement the columns with a sub bass loudspeaker The SUB option gives a sub bass output on the BCL port of the UT26 processors wiring is described in section 9 6 When using the SUB option the subwoofer signal is low pass filtered by the UT26 processor with a 4th order Linkwitz Riley type at 180 Hz and the column s signal is filtered with the complementary high pass filter Note that for speech diffusion there is no point extending the bass response 5 3 Sound Security System SSS The SSS option Sound Security System brings EN 60849 conformance to a StepArray system Itis suitable for installations diffusing security messages It consists of monitoring of proper functioning of the system as per the requirements of the norm using two daughter boards inside the UT26 processor and a sensor for electric current measurement Processor amplifier and speaker faults are detected Beyond the norm N The SSS option is a great way to ease maintenance of an installation by keeping you informed of proper fonctionning 6 SAdrive software The SAdrive software is primarly used to tune the operating parameters of Ste
29. n processor at a time Hardware options E cvzzz_ O mic Ose sss Column ouput on channels 4 to 6 Activate Model Sa 100P Name Group h I Add new processor Column ouput on danes 158 drive Model az Name sa250p 2 Group hal a An unused processor has been detected you can now specify its properties IF you don t want to use this processor unplug it from the BAN or shut it down To prevent conficts make sure to turn only one virgin processor at a time Hardware options cva32 mc sw sss Column ouput on channels 4 to 6 Activate Model S 190 Switch ON one more processor Remember Switch ON one processor at a time Save as boot setup to make all changes permanent Bil SAdrive 2 08 uu Active setup Presets Administration Help Discover from hardware setup Save as boot setup Manage processors Enter off line mode Add virtual processor y audio 11 2 Check connected processors 11 2 Check connected processors Already inited processors don t show up automatically in SAdrive To discover those processors follow the steps below Connect to COM port Discover from harware setup 1 i LA A Bi SAdrive 208 wee ws SA SAdrive 2 08 ne File Active setup Presets Administration Help File Activesetup Presets Administration Help Discover from hardware setup Choose COM port Save as boot setup R w SSS S n Manage processors sens ass
30. nnected to the command channel GND on pin 1 on pin 2 on pin 15 of the BAN connector In 7 this case the CV232 option is not needed 24 doute 9 6 SUB wiring 9 6 SUB wiring When the UT26 processor is equipped with the SUB option section 5 2 a sub bass output is delivered on the BCL port of the UT26 processor Table 6 describes the wiring used Pin Sig pin 5 pin 6 pin 14 Ground Table 6 SUB wiring on BCL port 10 Test before powering up Before powering up an installation it is good practice to ensure that the column cable is properly connected to the column Therefore the electrical resistance of each channel of the column must be controlled at the end of the cable connected to the amplifier side The measured electrical resistances values must correspond to the values below Channel 1 2 3 4 5 6 SA100P 6 60 6 60 6 60 _ SA180P 6 60 6 60 6 60 _ _ SA250P 6 60 6 62 6 6Q 4 40 440 4 40 SA400P 6 62 6 60 6 60 6 60 6 60 6 60 SA180S 6 60 6 60 6 60 _ SA250S 3 30 6 60 6 60 4 40 4 40 3 30 For details on connector pin assignement see figure 18 on page 23 4 When measuring the electrical resistance the cable resistance must be taken into account about 1 3 for C 100 meters of 1 5mm2 0 70 for 100 meters of 2 5mm Last update December 23 2010 25 Active
31. ns 14 and 15 30m Floor Figure 6 Listening zones P models 22m 28m Figure 7 Listening zones S models Columns whose name ends with a P SA100P for example are designed for horizontal audience areas whereas column whose name ends with a S are designed for tilted audience areas or with balcony 2 3 StepArray specificity shared electronics One of the advantages of using external electronics is that several columns can be connected via their amplifier to the same UT26 processor A UT26 processor features 6 analog symmetrical outputs Therefore a single UT26 processor can be used to deliver signals for a6 channel column one or two 3 channel columns Moreover a UT26 processor can be connected to one or several StepArray amplifiers to feed several columns with the same signal In this case the inputs are simply daisy chained to the amplifiers see section 9 1 on page 22 Last update December 23 2010 11 Aline audio In the example installation figure 8 three independant rooms are equipped with StepArray columns Each room receives its own signal and can have independant parameters For a total of 6 columns only 2 processors and 3 amplifiers are needed Lounge 2 x SA100P Conference room 2 x SA180S Hall 2 x SA250P SUB x SSSR 6 2x UT26 Essa 100000000 Lounge input Conference input Hall input Figure 8 Shared elec
32. null modem 24 V audio LIST OF FIGURES 21 22 23 24 25 26 27 28 29 30 31 32 33 Automatic gain control functional graph 27 Boe CANNE AAJA 2225 e a aa ae e SR ES EE te E a ee ee a a E ei 28 SA12 SW frequency response c c 4 4 eee ee Da Ra 34 StepArray column dimensions e e a 35 Fixing brackets for wall mounting of StepArray columns 36 Frequency response column SA250P 37 Horizontal directivity column SA250P 37 SAIOOP acoustical dala o o c 2 08 a hate RRR RR ee ek eo 38 SA180P acoustical data c coe o o o be kG es bn me Soe RU ae a se 39 SAZSOP acoustical Pata cos a PA ds eG Sages Re a 4 ee deu a 40 SAADOP acoustical dala o 6 A A E ee Be ee 41 SAPOS ACHUSICA alo 8 ace lng o AA i A E AR ut de 42 5A2506 acoustical EA cio ca a A Es un OA A ale 43 Last update December 23 2010 45 www activeaudio fr info activeaudio fr 332 Bd Marcel Paul CP602 44806 Saint Herblain Cedex France Tel 33 0 2 40 92 39 90 Fax 33 0 2 40 92 39 91 Contact
33. o channels 1 3 5 of both columns and amplifier 2 to channels 2 4 6 of both columns Easier maintenance all electronics can be easily accessed in the technical room e Electronics can be placed in a fireproof room with uninterruptible power supply UPS The operating parameters of the UT26 processors are tuned with the SAdrive software through RS232 serial communication UT26 processors feature filtering functions such as the control of directivity equalization delay and high level functions In addition the StepArray system features a set of options such as subwoofer output SUB active gain control AGC and security system supervision SSS 2 1 StepArray system example Figure 5 is an example of a complete StepArray installation The audio signal is fed into the UT26 processors which then supply DGRC compatible signals to the MPA6150 amplifiers A UT26 can also provide sub bass output when equipped with the SUB option The settings are made with the SAdrive software through an RS232 serial bus SA250P SA250P j LJ SA12 SWA 3x MPA6150 Peers pera 2x UT26 yy SAN ess on uso input Figure 5 Example of StepArray system 4x SA100P 10 y audio 2 2 StepArray column models 2 2 StepArray column models Table 1 on the next page and table 2 on page 13 give an overview of the StepArray models characteristics A complete description of the technical characteristics can be found in sectio
34. ound over the audience Indeed although a distributed public address system might yield a relatively constant SPL over the audience using a large number of loudspeakers it is usually not able to provide satisfactory speech intelligibility when reverberation in the room is high In addition it usually has a rather negative impact on the visual aspect of the room In contrast high speech intelligibility can be obtained with a limited number of loudspeaker arrays often only 1 or 2 in a large and highly reverberant room with minimum impact on the aesthetics of the room It is easy to calculate the shape of the wave front that should be radiated by a loudspeaker array in order to yield constant SPL over the entire audience area and minimize sound energy emitted elsewhere A J shape wave front is obtained in which the local curvature depends on the focal distance as illustrated on figure 2 In order to generate such a wave front one can align loudspeakers along the J shape as in geometric arrays figure 3a on the following page C HEIL or place loudspeakers on a vertical line and rely on the filtering of each individual loudspeaker as in electronic arrays figure 3b on the next page DSP directivity The latter case corresponds to column loudspeakers which can be flush mounted on a wall Advantages and disadvantages of both array types are discussed in DGRC Arrays X1 Listening plan X2 Figure 2 J shape wave front required in order to rad
35. pArray columns but it is also a great simulation tool The software can be downloaded for free on Active Audio s website http www activeaudio fr en gamme steparray sadrive 16 Active audio SAdrive provides access to a full range of operations including for each column e input selection with adujstable noise gate equalization 6 fully parametric biquadratic filtering elements sub bass output management delay e directivity control automatic gain control management These operations are directly accessible through the SAdrive Synoptic frame as shown on figure 12 gt mao Z Directivity e O tidar AGC Figure 12 Synoptic frame Additionally it is possible to save and recall operating parameters in presets The main feature of SAdrive is the directivity control block which allows the user to change the radiation pattern of StepArray columns in real time This block is presented in figure 13 Bi SAdrive 210 ELLES File Activesetup Presets Administration Help mm Structure gt A 3 gt z Sp 7 2 0m Leila Input Bass Equaizer Delay i AG Directivity a e Direct sound map Listening area 0 Vertical plane A orne kb Directivity control near fi far Spatial balance 0 0 Column height m 2 55 Focal min m 3 4 Focalmax m 18 1 OutRMS Ut26 Addr Name Model Group Status Signal Mu
36. red as described in section 9 5 on page 24 SAdrive does find the UT26 processor The UT26 processor is not equipped with the CV232 option Connect the UT26 processor through the BAN to a UT26 processor equiped with the CV232 option as explained in section 9 5 on page 24 The COM port selected in SAdrive is wrong Select the correct COM port in SAdrive Administration Choose COM port The processor is already inited Use menu Active Setup Discover from Hardware to discover inited processors see also section 11 2 on page 27 The sound is not homogeneous or distorted 30 Amplifier to column connection is incorrect Make sure columns are properly connected as described in section 10 on page 25 Aline audio Symptom Possible cause Input signal level is too high Solution Reduce input signal level Max signal input is 3 25V as described in 14 1 on the next page Filtering parameters are wrong Reduce the gain Mixer Block Correct the equalization The column is a pre 2010 column Check the tick box using the menu Active Setup Manage processors In the Options frame use more then specifiy if the column is a pre 2010 one There is a wiring problem Make sure the wiring is correct see 10 on page 25 The parameters of the Directivity block are wrong Check that listening area defined in the Directivity block of SAdrive matches
37. te Noise Clip Bus Err Level y 1 smog 10009 007 ece N x x ES w x EN ET AI A A A A Figure 13 SAdrive directivity block 7 CAD modeling There are powerful CAD software tools that can predict the acoustics of a room and accurately model the radiation of loudspeaker arrays These tools can calculate various acoustic index such as reverberation time sound pressure level STI In a loudspeaker array all loudspeakers operate in a coherent way This must be taken into account in the modeling To do so software modules DLL which enables the CAD tools to properly model the StepArray columns are included inCATT Acoustic and EASE Last update December 23 2010 17 V andio REFERENCES Figure 14 shows examples of a modeling results for CATT Acoustic and EASE O With the StepArray DLLs the directivity parameters can be adjusted as can be done in real situation with the SAdrive software 70 60 50 40 30 20 a Example of RASTI modeling using software CATT Acoustic b Balloon plot of SPL radiated in octave 1 kHz by column SA250S Simulation with EASE Figure 14 Examples of a CAD modeling results References DGRC Arrays X Meynial DGRC arrays A synthesis of geometric and electronic loudspeaker arrays AES 120th Convention Preprint 6786 Paris May 2006 C HEIL Sound Wave Guide US Patent 5 163 167 Inventor C Heil nov 10 1992 DSP directivity G
38. the following effects e red LED is turned ON on UT26 front panel processor beeps SSS contact between pins 1 and 9 is open on the BCL port of the UT26 processor is open If the UT26 processor fails the beep and LED signals won t work but the SSS contact will still be opened so that the failure is reported to the central monitoring system of the installation The SSS contact is the primary indication for failure it will be opened even if the processor fails on missing O power supply for example so that failure is always reported 4SSS contact is between pins 1 and 9 on the BCL port of UT26 processor Examples of malfunctions _a column channel is disconnected from the amplifier e amplifier is off again on the amplifier was changed by mistake a loudspeaker burned e the column cable is cut e etc 12 3 Feedback killer The feedback killer used in the UT26 processors is a modulated delay The delay is modulated sinusoidally with a constant depth of 2 6ms while the modulation frequency is adjustable for more or less agressive feedback elimination The variation frequency is as follows Off no modulation e Low 0 6H z modulation frequency Mid 1 3H z modulation frequency e High 4 0H z modulation frequency On site measurements indicate that the gain margin can usually be increased by 4dB e The feedback killer maybe used for speech diffusion but should be switched
39. tronics example 3 Choosing the right installation set up 3 1 Columns All StepArray columns feature a large frequency bandwidth and a wide horizontal opening angle The columns are mounted vertically using the supplied square brackets The columns are available in standard RAL colors RAL9016 and RAL9005 but any other RAL color is available with the COL option Table 1 sums up these charac teristics Max SPL Hor opening Bandwidth Mounting Colors 95dBg pr 180 135Hz 17kHz 3dB Vertical White RAL9016 pink noise 6dB 110Hz 19kHz 10dB supplied Black RAL9005 in listening area square brackets Any RAL COL option Table 1 General characteristics of StepArray columns StepArray columns do not use opening angle and tilting angle to tune directivity Instead StepArray use the listen ing area definition to automatically adjust themselves as to fit the requirements to the best O Aa StepArray columns use the listening area definition to automatically adjust themselves 3The horizontal opening angle corresponds to a 6dB attenuation for the average of the 1 kHz and 2 kHz octaves 12 L V audio 3 2 Processors The StepArray range provides a full set of listening ranges and audience tilting angles to suit any public address situation The listening areas as described on figure 9 are listed on table 2 The nominal situation corresponds to the conditions for which the column has be
40. utput impedance 46 Q Dynamic range 95 dB Sub bass output option Symmetrical output on DB25 female BCL port 4th order Likwitz Riley lowpass filter at 180Hz Max output voltage 1 6V 3 3dBU General data Communication RS232 port at 38400 bauds Mains 230V 50Hz 15W max Power consumption 45W Dimensions 430 x 44 x 285mm Rack 19 1U Color Black Weight 4kg 32 Aline audio 14 2 MPA6150 amplifier characteristics 14 2 MPA6150 amplifier characteristics Audio data Operating modes 6 independent channels 3 independent channels bridged 2 x 3 channels ini out 1 2 3 in2 out 4 5 6 Power 6 x 100 W under 8Q 6 x 150W under 42 3 x 300W under 8Q bridged Power consumption Typical 100W Max 1kW Analog inputs 6 symmetrical analog inputs Phoenix connectors Outputs 6 outputs on screw terminals Frequency response 20Hz 20kHz 1W 1dB Input Impedance 10kQunbalanced 20kQ balanced Sensitivity Ves Signal to noise ratio 95dB Damping factor gt 300 Gain Adjustable with 6 knobs on rear panel Max voltage gain 28dB Harmonic Distortion THD 0 1 1kHz General data Cooling Variable speed fan Protection Protection against overload and overheat Indicators Clip and Protect LEDs Dimensions 483 x 88 x 420mm Rack 19 2U Weight 12 3kg
41. watts under 42 load or 6 x 100 watts under 8Q loads More details on wiring can be found in section 9 1 The range of a column is defined as the maximum distance from the column for which the mean sound level for the octaves 500Hz 1 kHz and 2 kHz remains within 3dB or 5dB Last update December 23 2010 13 y audio 3 4 Cables 3 4 Cables Cable lengths detailed in table 3 correspond to the maximum lengths recommended for the amplifier to column cable Cable length Wire diameter lt 300m 1 5mm lt 500m 2 5mm Table 3 Wiring recommendations for StepArray columns For very long distances exceeding the maximum cable length mentioned in table 3 please contact Active Audio e 3 channel columns need a 4 wire cable e 6 channel columns need a 7 wire cable 3 5 Subwoofers In cases where the StepArray system diffuses music the sound fidelity will be better if a subwoofer and its associated amplifier are added This option is not necessary for installations aimed at vocal diffusion since the human voice hardly has component frequencies in the bass range below 150 Hz The subwoofer signal is delivered by an UT26 processor fitted with the SUB option see section 5 2 Active Audio proposes subwoofers SA12 SW and SA12 SWA suitable for StepArray installations see section 14 3 4 Column positionning rules When choosing a StepArray setup the goals are
42. y poor intelligibility and value 1 corresponds to perfect intelligibility It is generally considered that intelligibility is correct above STI 0 55 Energy of the reverberated field is proportionnal to the ratio Reverberation time Room volume V audio 1 2 Loudspeaker arrays IN Using many non directional loudspeakers often leads to poor intelligibility all loudspeakers contribute to the reverberation while only a few contribute to direct sound Using highly directionnal loudspeakers is an easier solution in large spaces because only few diffusers are needed In addition to improved acoustic performance and reduced cost it minimizes the aesthetical impact of the public address system Sound quality Intelligibility is not enough for good perceived sound quality Another very important aspect is that every listener has an adequate sound pressure level SPL which implies that the public address system provides an even coverage of the audience area This can be acheived with an accurate control of the loudspeaker directivity Acoustic comfort also implies a wide frequency bandwidth and low harmonic distortion The most important goal of a public address system is to provide a strong and constant direct sound over the entire audience area and minimize the energy emitted elsewhere 1 2 Loudspeaker arrays Loudspeaker arrays are often the best solution to providing strong and constant direct s
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